The NWRA Classification Infrastructure: Description and Extension to the Discriminant Analysis Flare Forecasting System (DAFFS)

A classification infrastructure built upon Discriminant Analysis has been developed at NorthWest Research Associates for examining the statistical differences between samples of two known populations. Originating to examine the physical differences between flare-quiet and flare-imminent solar active regions, we describe herein some details of the infrastructure including: parametrization of large datasets, schemes for handling "null" and "bad" data in multi-parameter analysis, application of non-parametric multi-dimensional Discriminant Analysis, an extension through Bayes' theorem to probabilistic classification, and methods invoked for evaluating classifier success. The classifier infrastructure is applicable to a wide range of scientific questions in solar physics. We demonstrate its application to the question of distinguishing flare-imminent from flare-quiet solar active regions, updating results from the original publications that were based on different data and much smaller sample sizes. Finally, as a demonstration of "Research to Operations" efforts in the space-weather forecasting context, we present the Discriminant Analysis Flare Forecasting System (DAFFS), a near-real-time operationally-running solar flare forecasting tool that was developed from the research-directed infrastructure.Comment: J. Space Weather Space Climate: Accepted / in press; access supplementary materials through journal; some figures are less than full resolution for arXi

Rapid learning of pursuit target motion trajectories revealed by responses to randomized transient sinusoids

When humans pursue sinusoidal target motion they rapidly learn to track with minimal phase error despite inherent visuo-motor processing delays; prior evidence suggests that prediction might even occur within the first cycle. Here, this has been examined by evoking reactive responses to single cycle stimuli having randomised periodicity and peak velocity. Periodicity was varied within three specific ranges with differing average periodicity. Initial responses in the first half-cycle were remarkably similar within periodicity ranges, irrespective of target velocity or frequency, but differed between ranges. In contrast, in the second half-cycle eye velocity closely matched the target in velocity and timing, irrespective of differences in eye velocity in the first half. Abrupt transitions occurred between first and second half-cycles, consistent with the hypothesis that target motion information is sampled and stored within the first half-cycle, irrespective of actual eye velocity evoked, and then released as a predictive estimate in the second half

Achieving Consistent Doppler Measurements from SDO/HMI Vector Field Inversions

NASA's Solar Dynamics Observatory is delivering vector field observations of the full solar disk with unprecedented temporal and spatial resolution; however, the satellite is in a highly inclined geostationary orbit. The relative spacecraft-Sun velocity varies by $\pm3$~km/s over a day which introduces major orbital artifacts in the Helioseismic Magnetic Imager data. We demonstrate that the orbital artifacts contaminate all spatial and temporal scales in the data. We describe a newly-developed three stage procedure for mitigating these artifacts in the Doppler data derived from the Milne-Eddington inversions in the HMI Pipeline. This procedure was applied to full disk images of AR11084 to produce consistent Dopplergrams. The data adjustments reduce the power in the orbital artifacts by 31dB. Furthermore, we analyze in detail the corrected images and show that our procedure greatly improve the temporal and spectral properties of the data without adding any new artifacts. We conclude that this new and easily implemented procedure makes a dramatic improvement in the consistency of the HMI data and in its usefulness for precision scientific studies.Comment: 58 pages, 19 figures, submitted to Ap

The role of productive replication in the pathogenesis of murine gammaherpesvirus-68

Murine gamaherpesvirus-68 (MHV-68) is natural pathogen of small free living rodents. Like Epstein-Barr virus, MHV-68 is B-cell tropic with respect to latency and sensitive to the anti-viral acyclovir (ACV). The aim of this project was to evaluate the potency of a new anti-viral called 2'-deoxy-5-ethyl-ß-4'-thiouridine (4'- s-EtdU) as an inhibitor of MHV-68 replication both in vitro and in vivo. Finally to utilise the anti-viral activity of 4'-s-EtdU, to be able to study disease associated with gammaherpesvirus latency in immunocompromised mice, without the complications associated with lytic virus replication. The potency of 4'-s-EtdU as an inhibitor of the lytic replication was determined to be 15 times greater than ACV by EC₅₀ assay, giving a value of 0.13μM (35ng/ml). Treatment of infected cell lines lead to the elimination of detectable productive viral replication. However, virus genomic DNA, which remained capable of reactivation after treatment withdrawal, was not eliminated. Not only was this true for cell lines which MHV-68 is known to establish latency, but also cell lines previously known only to support lytic replication. The nature of the viral persistence appeared different for the different cell lines both with respect to virus reactivation after withdrawal of treatment and to the spontaneous generation of 4'-s-EtdU resistant viral variants. The data leads to the possibility of MHV-68 being capable of episomal maintenance whilst in a perpetual state of attempted productive replication. Spontaneously arising 4'-s-EtdU resistant virus variants were cloned and isolated and found to remained sensitive to the anti-viral effects of ACV. However, further characterisation of these viral variants was not undertaken. Treatment of mice with 4'-s-EtdU (0.3mg/ml in drinking water) from 3 days post infection (in), rapidly eliminated productive virus replication in the lung tissue, but failed to prevent the establishment and long-term maintenance of viral latency in the lymphoid compartments. Treatment also failed to prevent the post acute splenomegaly commonly observed in MHV-68 infected mice. However, prophylactic treatment of mice prior to infection (in), did prevent virus dissemination to the spleen as well as preventing splenomegaly. Viral DNA remained absent from the spleen for as long as treatment was maintained, up to 54 days post infection, as determined by both co-cultivation assay and nested PCR. However, virus DNA was detected in the lung tissue of the same mice. Dissemination of virus to the spleen, on withdrawal of treatment correlated with the production of MHV-68 specific antibodies, as determined by whole virus ELISA. The experiments provided evidence for both chronic and latent infections of the lung tissue of the mice infected via the intra-nasal route. The evidence demonstrated the importance of productive virus replication in the establishment of viral latency in circulating B-cells and hence development of IM like syndromes even when MHV68 was administered via the intra-peritoneal route. Although 4'-s-EtdU treatment protected SCID mice from an otherwise lethal MHV-68 infection, it was not possible to determine the role of productive virus replication in oncogenesis since lymphomas failed to develop in both long-term infected transiently immunosuppressed, C57BL/6 mice and in SCID mice recipients of syngeneic splenocytes. The study failed to reproduce the earlier studies (Sunil-Chandra et al, 1993). Surprisingly, viral latency appeared to be maintained in normal healthy BALB/c mice more efficiently than in SCID mice transiently repopulated with BALB/c splenocytes. Hence it was not possible to investigate either the therapeutic benefit or establish the role of productive virus replication in the development of MHV-68 associated tumour

Interactive Visualization of the Largest Radioastronomy Cubes

3D visualization is an important data analysis and knowledge discovery tool, however, interactive visualization of large 3D astronomical datasets poses a challenge for many existing data visualization packages. We present a solution to interactively visualize larger-than-memory 3D astronomical data cubes by utilizing a heterogeneous cluster of CPUs and GPUs. The system partitions the data volume into smaller sub-volumes that are distributed over the rendering workstations. A GPU-based ray casting volume rendering is performed to generate images for each sub-volume, which are composited to generate the whole volume output, and returned to the user. Datasets including the HI Parkes All Sky Survey (HIPASS - 12 GB) southern sky and the Galactic All Sky Survey (GASS - 26 GB) data cubes were used to demonstrate our framework's performance. The framework can render the GASS data cube with a maximum render time < 0.3 second with 1024 x 1024 pixels output resolution using 3 rendering workstations and 8 GPUs. Our framework will scale to visualize larger datasets, even of Terabyte order, if proper hardware infrastructure is available.Comment: 15 pages, 12 figures, Accepted New Astronomy July 201